Presently, gas and liquid chromatographs are the most routinely used instruments in analytical and clinical laboratories for the analysis of organic compounds. The objective of Lee Scientific is to manufacture an instrument which uses supercritical fluids instead of gases or liquids as mobile phases. The ability to significantly affect solute solubility in the supercritical fluid mobile phase by changes in operating pressure is the fundamental principal on which capillary supercritical fluid chromatography is based. Of key importance is the improved analysis of high-molecular-weight, polar, or thermally unstable compounds. Therefore, cellular constituents may be more amenable to analysis by SFC than by either GC or LC. Furthermore, preliminary work indicates that these high-molecular-weight and polar biological molecules may be detected by direct injection into mass spectrometers or other detectors normally only available to volatile compounds. This proposal addresses the advantages of supercritical fluids versus gases or liquids in chromotographic instruments and proposes to evaluate the potential of the commercial development of capillary SFC interfaces for chromatographic detectors such as ionization, electron capture, spectrophotometric, and mass spectrometric detectors. The SFC system developed will be optimized for molecules of the type which are of significance in studies of cellular functions and structure.